Original equipment manufactured (“OEM”) manifolds for channeling air flow between a compressor, such as a turbocharger outlet and the air intake of an internal combustion engine frequently provide less then optimum fluid flow characteristics thereby preventing the engine from achieving optimum performance.
An example of such sub-optimal performance is the OEM or stock intake manifold for the 2003-2007 Dodge Ram Commonrail® engine trucks utilizing tubrocharged Cummins® 5.9L diesel engines. The engine's air intake or opening port (positioned below the manifold) is connected to the outlet of the turbocharger's intercooler via a bellows type hose and hose clamp identified in the photo. The manifold's outlet is secured over the engine's air intake opening via bolts or screws as shown.
The stock manifold was (and still is) deficient in several aspects, e.g., in providing a limited cross-sectional area for air flow and in its mounting arrangement for securing the outlet end to the engine air intake plate. The latter deficiency results from the pinched-in-sides of the manifold adjacent the outlet end which accommodate the two manifold/engine air intake mounting screws closest to the turbocharger (“proximal mounting screws”).
One setting out to replace a stock component such as the above intake manifold faces certain constraints. In addition to cost and head room, i.e., distance to the hood, the position (and orientation) of the turbocharger's outlet and the engine's air intake port come into play. In this example, the air intake port (rectangular in shape) is formed in a horizontal section of a plate bracketed by two proximal threaded blind bores (nearest the turbocharger) and two opposed distal threaded bores (remote from the turbocharger). The threaded bores are arranged to receive mounting screws to hold the manifold in place,. The turbocharger outlet is circular and oriented at a compound angle of about 60° to the horizontal plane of the intake port and about 25° to a vertical plane. The stock manifold is basically in the form of a rectangular tube with a 90° bend adjacent the engine air intake, joined to the turbocharger outlet through the 60°/25° compound curve. The 90° bend presents a challenge, particularly where (as in the case with the stock unit) the radius of the bottom (or inner) wall is considerably smaller than the radius of the top (or outer) wall at the bend.
Absent the constraints pointed out above, the velocity distribution through the bend could be considerably improved, resulting in a decreased impedance to air flow and pressure drop, by using the same radius for both the inner and outer walls and adding turning vanes in the bend. (“Heat Exchanger Design” by Arthur F. Frass, 2nd Edition, published by John Wiley & Sons, Inc., 1989, pages 158-161).
The ATS manifold may provide an increased cross-sectional area for air flow and provides a somewhat larger inner radius at the 90° bend. However, to accomplish this, the manifold outlet opening (at the discharge end) is enlarged requiring that the proximal mounting screw extend from screw supporting seats, recessed into the upper side walls, along the side walls of the manifold. The resulting seat accommodating recesses, though smaller than the pinched-in-sides of the stock version, and the proximal mounting screws shafts extending inside the manifold still create a significant flow restriction resulting in less than optimum performance.
The Banks manifold eliminated the manifold pinched-in-side effect by forming apertured recessed seats for the heads of the proximal mounting screws on the top of the manifold with the shafts of the screws again extending through the interior of the manifold. The screw shafts as well as the inwardly protruding seats (to form a pleasing outside appearance) interrupt and impede the air flow resulting in less than optimum performance. Both the ATS and Banks manifolds are formed of cast aluminum.
Another aftermarket manifold marketed under the CFM+ logo is made of a plastic composite material with the claim that the composite has a smoother surface than cast aluminum and therefore produces less turbulence and a lower pressure drop. While the manufacturer claims that the CFM+ manifold provides a 44% increase in air flow over the stock unit and a 22% increase over the Bank's unit, it is not believed that the testing was measured using a predetermined pressure differential, e.g., 1.5″ H20 across the manifold. Moreover, plastic (while perhaps providing less restriction to air flow) is a relative poor thermal conductor as compared to aluminum. Under many driving conditions the air exiting the turbocharger intercooler is hotter than the engine compartment air surrounding the air intake manifold. The superior thermal conductivity of aluminum (versus plastic) allows the manifold to function as a heat exchanger to remove some heat from and thereby cool the air entering the engine air intake.
In addition, the CFM+ proximal mounting screws are secured in seats located externally of the manifold which limits the maximum size of the manifold's outlet opening and the effective inner radius of the manifold at the 90° bend.
Also, there is a questions of strength of materials. Given the same wall thickness it is our opinion that aluminum is stronger than the CFM+ plastic composite.
There is a need for a more efficient air intake manifold for the referenced vehicle (and other vehicles exhibiting like characteristics) which not only provides an optimum air flow rate, but functions as a heat exchanger to provide some cooling effect for the air entering the engine air intake.